The heritage wheels are steel, and just looking at them they appear to have a lot more mass, so I would be pretty sure they weigh a good amount more than your 19" aluminum wheels do. As for spoiler, thats not going to add very much weight, maybe 10 lbs at most. Heated seats I could definitely see adding more weight, however the very slight weight differences between LS, 1LT, and 2LT aren't going to add up to very much performance-wise.
But yes, the LLT engine is beautiful and I definitely have no trouble at all having fun in this car
